# lazySource

Defers creation and materialization of a `Source` until there is demand.

@ref[Source operators](../index.md#source-operators)

@@@div { .group-scala }

## Signature

@@signature [Source.scala](/akka-stream/src/main/scala/akka/stream/scaladsl/Source.scala) { #lazySource }

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## Description

Defers creation and materialization of a `Source` until there is demand, then emits the elements from the source
downstream just like if it had been created up front.

See also @ref:[lazyFutureSource](lazyFutureSource.md).

Note that asynchronous boundaries (and other operators) in the stream may do pre-fetching which counter acts
the laziness and will trigger the factory immediately.


## Reactive Streams semantics

@@@div { .callout }

**emits** depends on the wrapped `Source`

**completes** depends on the wrapped `Source`

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